This invention relates to an air-conditioning control apparatus on board vehicles such as automobiles and more particularly to a vehicle air-conditioning control apparatus capable of properly correcting changes in sensible temperature within the vehicle room which are due to changes in the sunlight ray incident to the interior of a vehicle.
The sensible temperature within the room of a vehicle, for example, an automobile greatly changes depending on an incident condition of the sunlight ray. Accordingly, in order to maintain a comfortably air-conditioned state, it is desirable that a temperature distribution on a horizontal plane within the room be controlled in accordance with a condition of the sunlight ray incident upon the automobile. The controlling of the temperature distribution is called sunlit illumination correction.
Incidentally, sunlit illumination correction is adopted in conventional air conditioners as described in, for example, Japanese Utility Model Unexamined Publication Nos. (JU-A) 58-36912 and JP-A-60-179321. In JU-A-58-36912, a plurality of photoelectric conversion elements are employed which are arranged to receive the sunlight ray at different incident angles, a larger output signal is selected from output signals, responsive to sunlit illumination amounts, of the conversion elements, and the air conditioner is operated for temperature control on the basis of the selected signal. The photoelectric conversion element has poor sensitivity to an obliquely incident ray but the use of the plurality of photoelectric conversion elements can prevent inconvenience of inaccurate measurement of the sunlit illumination amounts. Therefore, this prior art apparatus does not intend to detect a direction in which the sunlight ray irradiates the vehicle body.
In No. JP-A-60-179321, a plurality of photoelectric conversion elements are arranged at various locations of the vehicle body, the magnitude relation among output signals of the photoelectric conversion elements is used to decide whether the sunlight ray irradiates the righthand side or lefthand side of the vehicle body, and amounts of air fed to respective air discharge ports provided at various locations within the room are controlled in accordance with a decision result.
Thus, the latter prior art apparatus performs air-conditioning control by merely detecting whether the sunlight ray irradiates the righthand side or lefthand side of the body. This prior art apparatus therefore fails to take into consideration air-conditioning control which can follow slight changes in sunlit illumination direction and faces a problem that it is unsatisfactory for achieving sufficiently comfortably controlled air conditioning.
The sunlit illumination correction mentioned hereinbefore is needed because many automobiles have a roof and the sunlit illumination amount applied to the righthand seat of the vehicle differs from that applied to the lefthand seat, depending on the sunlit direction. However, the difference in the sunlit illumination amount not only depends on whether the sunlit illumination direction is toward the righthand side or lefthand side of the vehicle but also is affected by an angle of the sunlight ray makes to the righthand side or lefthand side of the vehicle and by an angle of elevation of the sun relative to the horizontal plane of the vehicle.
This accounts for the fact that only the decision as to whether the sunlit illumination direction is toward the righthand side or lefthand side of the vehicle is insufficient to maintain a sufficiently comfortably air-conditioned state.